Conventionally, an electromagnetic load driving device that drives an electromagnetic induction load, includes a switching element (e.g., relay element) that interrupts an energizing current supplied to the electromagnetic induction load. A failure of a relay disables load control from continuing normally, and thus the electromagnetic load driving device typically performs failure diagnosis to the relay.
PTL 1 discloses the following technique for “enabling, in an inductive load driving device including two switching elements provided in series on an energizing path, an on-failure of each switching element to be detected even during energizing control”. “In energization-zero control in which a target current is zero (S140: NO) during normal control with a configuration including a duty driving transistor T10 provided on the upstream side of a linear solenoid and a fail-safe transistor T20 provided on the downstream side of the linear solenoid, the duty driving transistor T10 continues duty driving in arbitrary duty cycle and the fail-safe transistor T20 turns off, to make the energization zero (S260), instead of making the duty cycle of the duty driving transistor T10 zero to make the energization zero. If an energizing current is not zero at this time, it is determined that the fail-safe transistor T20 has on-failed (S300) (refer to abstract).”